Raising the X
09-11-2009, 10:54 PM
#1
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Raising the X
Hi - I have a 1992 34 SCARAB.
I have installed IMCO 2 inch shorties and am currently running 28 Bravo 4 blades ( not labbed )
Best speed I have seen GPS is 83 at 5600 RPM
80 at 5400. I have 509's that put out approx. 650 HP give or take a few. The prop shaft is now 4 inches below the hull. The question I have is I am thinking on raising the drives another inch maybe 2.
If I go to Maximus props at that height do you think I will have problems getting on plane?
Right now with the Bravos I just push the throttles untill about 4500 to 5000 RPM and the boat just comes on plane. The props dont blow out they just slip untill you get going and they hook up - then the boat takes off like a rocket. This takes about 3 seconds.
When the boat was stock ( 502's and 385 HP each ) the boat had 25 pitch Mirage 3 blades and if you took off too fast the props would blow out and you would have to try again slower.
I have been thinking of adding stand off boxes and going up at least 3 inches.
I haven't been able to find anyone that has added boxes to a 34.
This boat is not the same as the older SCARAB III.
I don't know the differance but it is about 10 MPH faster with the same HP.
Will I be able to get the boat on plane with the higher X ?
I have cable trim ind. - neutral trim is 3.
I have to trim to 9 for max speed.
I am hoping raising the X will keep the trim setting down to a reasonable setting.
Is there a rule of thumb? Adding a blade you can raise X this much and have the same traction.
Thanks Steve W.
I have installed IMCO 2 inch shorties and am currently running 28 Bravo 4 blades ( not labbed )
Best speed I have seen GPS is 83 at 5600 RPM
80 at 5400. I have 509's that put out approx. 650 HP give or take a few. The prop shaft is now 4 inches below the hull. The question I have is I am thinking on raising the drives another inch maybe 2.
If I go to Maximus props at that height do you think I will have problems getting on plane?
Right now with the Bravos I just push the throttles untill about 4500 to 5000 RPM and the boat just comes on plane. The props dont blow out they just slip untill you get going and they hook up - then the boat takes off like a rocket. This takes about 3 seconds.
When the boat was stock ( 502's and 385 HP each ) the boat had 25 pitch Mirage 3 blades and if you took off too fast the props would blow out and you would have to try again slower.
I have been thinking of adding stand off boxes and going up at least 3 inches.
I haven't been able to find anyone that has added boxes to a 34.
This boat is not the same as the older SCARAB III.
I don't know the differance but it is about 10 MPH faster with the same HP.
Will I be able to get the boat on plane with the higher X ?
I have cable trim ind. - neutral trim is 3.
I have to trim to 9 for max speed.
I am hoping raising the X will keep the trim setting down to a reasonable setting.
Is there a rule of thumb? Adding a blade you can raise X this much and have the same traction.
Thanks Steve W.
09-12-2009, 09:58 AM
#2
Charter Member #601
Charter Member
Steve,
I dont think those B1's will hold up to a maximus 5 blade prop.
The stand off box will help with the excessive trim, but raising the X may hurt your bow lift?? Of course I am talking in general terms here.
Let's hope someone has done it to this hull and can give you feed back..
Dick
I dont think those B1's will hold up to a maximus 5 blade prop.
The stand off box will help with the excessive trim, but raising the X may hurt your bow lift?? Of course I am talking in general terms here.
Let's hope someone has done it to this hull and can give you feed back..
Dick
09-12-2009, 10:41 AM
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I think a lot of that answer depends on how much hook is in the hull now. If there is any I would work on that next then consider going up more in prop shaft height if the trim needed is still high.
09-12-2009, 11:19 AM
#4
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For that year/size boat sounds like your doing very well. Is your HP form a dyno or guesstimate? Your best bet is to talk to BBlades or Throttle Up and work on the props or try different props. Might be able to squeeze a few more mph. Any drastic changes are going to cost alot and may not yeild the anticipated results.
Not sure of your planing technique, but @ 4500+ rpm is hard on the drives. Keep it under 3000 and let nature take it's course!! If you have some blowout and need the extra rpm to keep it going then that's ok.
Not sure of your planing technique, but @ 4500+ rpm is hard on the drives. Keep it under 3000 and let nature take it's course!! If you have some blowout and need the extra rpm to keep it going then that's ok.
09-12-2009, 11:46 PM
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Thread Starter
Pure energy - There isn't any blow out - they just slip for about 2 seconds while the boat takes off and then they hook up and off you go. The HP is the same as another engine with the same work done that was dyno'd.
There isn't any hook in the bottom at all. The bottom has been straightened and the corners sharpened.
Dick T. - If I raise the drives then I shouldn't have any more load on the drives than I have now with the 4 blades.
I intend to go with larger prop shafts.
Oh - And let you do your tricks to them.
There isn't any hook in the bottom at all. The bottom has been straightened and the corners sharpened.
Dick T. - If I raise the drives then I shouldn't have any more load on the drives than I have now with the 4 blades.
I intend to go with larger prop shafts.
Oh - And let you do your tricks to them.
